The controlled-impedance tag has no wiki summary.
4
votes
2answers
152 views
Why Characteristic Impedance must be “50” ohms?
Where does this number came from?
For single ended it must be 50 ohm and for differential pairs 100 ohm. Why?
For PCB with controlled-impedance these are that common numbers. Outside of the PCB you ...
5
votes
2answers
116 views
Can I slow a CMOS output through an RC filter?
Is it good practice to slow down the slew rate of a CMOS output by putting an RC filter on it? What happens with impedance matching after I do this? Or can I just set the RC filter with such a low ...
11
votes
1answer
251 views
Reasoning behind Ethernet pair order
An Ethernet connector seems to use a surprising choice of signal placement in its RJ45 connector. Does anyone know the reasoning behind:
The decision to make pair 2 straddle pair 1?
Why Ethernet ...
2
votes
1answer
188 views
Signal reflections at the driver?
This question is related to How do I use directional couplers on a differential signal?
I understand that if I have an impedance mismatch at the end of a signal cable, E.G. from a terminator which ...
6
votes
3answers
569 views
DDR1 Layout Considerations - DOs and DONTs
I am novice to high speed design.
Before getting in to DDR, I recently learned about impedance matching and how it is done, likewise I learned about length matching and how it is done.(Baby steps ...
6
votes
3answers
415 views
Controlled impedance in presence of vias and through-hole components (PTHs)
We have some controlled impedance traces on layer 4 of a board. Layer 3 is a GND plane. Layer 5 is a 3.3V plane. Both planes are unbroken (they occupy the entire layer), with the exception of vias and ...
1
vote
2answers
632 views
When does controlled impedance on a PCB matter?
Suppose I have a PCB that contains a microprocessor, or an FPGA (a "controller"). This "controller" drives a single-ended signal to an LVDS driver IC and a single-ended signal to a connector that goes ...
